Embodiments of the inventive concepts disclosed herein are directed generally to a system for providing stall recovery guidance to an aircraft pilot or crew via responsive symbology displayed via a head-down display (HUD), a head-up display (HUD), or a head-worn display (HWD).
In 2009, Air France Flight 447, an Airbus A330 out of Rio de Janeiro, crashed into the Atlantic Ocean after entering a high-altitude stall from which the aircraft never recovered. The aircraft's angle of attack (AoA) approached 40 degrees at one point and largely remained well above 30 degrees, rendering airspeed indications and stall warnings invalid. The aircraft remained in a stalled condition as it began to rapidly descend from cruising altitude, pitched upward at around 16 degrees, its engines responsive to command and continuing to develop full forward Takeoff/Go-around (TOGA) thrust until the craft struck the ocean surface.
As a result of the Air France crash, FAA training regulations were revised to include stall recovery procedures, applicable broadly to aircraft of all sizes or types and generally to any stall conditions, that prioritize the reduction of AoA above achieving maximum TOGA thrust. The stall recovery procedures provide for disengaging the aircraft autopilot or autothrottle system while maintaining altitude and preventing the aircraft pitch from changing adversely (e.g., in a nose-up direction). The pilot's priority is to reduce AoA via nose-down pitch control or stabilizer trim (if necessary) while keeping the wings level (roll control). Thrust may be adjusted accordingly as needed; maximum thrust may not always be advised as the application of maximum thrust may create a nose-up pitch moment (e.g., for aircraft with engines mounted below the wing) and exacerbate a stall condition.
Current HUD symbology may complement the situational awareness provided by the primary flight display (PFD) by offering recovery guidance under windshear or unusual-attitude conditions. Current symbology may indicate a stall or near stall condition to the pilot, but does not provide active guidance for stall recovery.